I don't understand why so many people are hung up on flying cars. It's a huge increase in the energy it takes to get from point A to point B, and for what reason? What do they hope to gain by wasting so much more fuel?
The only conceivable way I could see flying cars being a 'thing' is if we carved out 'air roads' for them that didn't cross over buildings or other cars. At that point, what's the benefit?
Also, if we do get flying cars, it'll probably be in part because of a drastic reduction in energy use of flying over driving (e.g. reducing the energy gap between flying and driving).
I think however, in most regards, making almost all cars self-driving will bring most of the benefits
On the other hand, you'll never get a flying car because FAA regulations form a moat around widespread cheap aircraft. A 40 year old Cessna 172 can only have an engine provided by Lycoming, can only be overhauled or repaired with Lycoming and Cessna parts, and can only be serviced by FAA certified mechanics (even though the design is only slightly more sophisticated than a VW aircooled engine and is based on 1930's technology).
[1]: https://www.quora.com/How-many-miles-per-gallon-mpg-does-a-C...
FAA regulations for certified aircraft are indeed a huge hurdle on progress, but are not at all a hurdle for experimental aircraft (which is where flying cars are today). (Side note: private aircraft owners flying under part 91 [roughly: not charter, not airline] are allowed to produce or cause to be produced "owner produced parts", so not all parts need to come from the OEM. It plays out that most engine parts do, but many airframe, interior, etc parts do not.)
For me the flying car is a solution in search of a problem. When I fly somewhere, there are almost always rental cars (or rideshares) widely and easily available. I don't want to take my lightweight, expensive, and somewhat damage-sensitive airplane into traffic 600 miles from home where a fender bender leaves me unable to fly home. That's what a rental car is for.
Would it be nice to land in my own "car" and immediately drive to my ground-bound destination without having to unpack/repack? Sure.
Am I willing to accept the inherent compromises, expenses, and risks implied by that? Absolutely not.
Do I think the market is? Nope.
And quad copters are pretty dang inefficient (as are helicopters in hover mode), making the energy hurdle higher than fixed wing (or translational helicopter) flight.
Quads might end up being part of the solution (and I admit I hadn't considered them before, so thanks!), but I don't think they're well suited for covering significant distances, which is presumably where the appeal of a flying car is strongest.
As for efficiency, yes, no simple solutions there. Note that they can still have fixed wings, the hover mode is only necessary for take off/landing.
[1]: https://www.aopa.org/about/general-aviation-statistics/activ...
And I imagine people like the idea of going as the crow flies, shorter travel times, no traffic congestion and not having to fuss over road construction.
And since it's just a flight of fancy they don't have to consider the risks of falling out of the sky, mid air collisions, noise pollution, increased energy consumption, severe weather, running out of fuel, running out of fuel over Lack Michigan or the Atlantic Ocean or the human factor of letting people who can barely handle X and Y also deal with Z.
Maybe some people just have general optimism that the imagined benefits outweigh the obvious problems.